function compare(propertyName) {
	return function (object1, object2) {
		var value1 = object1[propertyName];
		var value2 = object2[propertyName];
		if (value2 > value1) {
			return -1;
		}else if (value2 < value1) {
			return 1;
		}else {
			return 0;
		}
	}
} 
function compare_desc(propertyName) {
	return function (object1, object2) {
		var value1 = object1[propertyName];
		var value2 = object2[propertyName];
		if (value2 < value1) {
			return -1;
		}else if (value2 > value1) {
			return 1;
		}else {
			return 0;
		}
	}
} 
